In prior art, a magnetoresistive sensor device ("magnetoresistive head") typically has comprised a piece of magnetoresistive material through which a constant current I was driven, while it was arranged in physical proximity to a magnetic medium, such as a ribbon or wire, in which bits of information data were stored. Each of the bits typically was manifested by a magnetic orientation or magnetic pole strength of a localized magnetized region of the medium. As magnetic medium was moved such that different regions in succession were in closest proximity to the piece of magnetoresistive material, a change in voltage V across the piece of magnetoresistive material is developed in accordance with the resulting succession of bits that had been stored (and remain stored) in the medium. In this way a magnetoresistive sensor device was formed, with the voltage V measured as a function of time t, thus indicating the spatial sequence of bits stored in the medium. The device thus (nondestructively) can read the information contained in the medium. The device was called a "magnetoresistive transducer" because it thus convened a stream of magnetic information into a stream of electrical resistance (=V/I) information.
For example, U.S. Pat. No. 5,206,590 describes a magnetic sensor comprising a structure including a first and a second thin film layer of ferro-magnetic materials separated by an intermediate thin film layer of a non-magnetic metallic material. The first thin film layer is magnetically soft relative to the second thin film layer. However, although operative, such a structure involves complex and expensive processing of the layers.